Currently, well-recognized, yet unexplained age and sex related differences in age-associated lung disease may reflect actions of gonadal hormones and/or genes encoded on the sex chromosomes. The gap in knowledge addressed in this proposal centers on whether this sex disparity is due to activational effects of gonadal hormones (differential effects due to estrogen or testosterone) and/or sex chromosome complement. This proposal has high impact since sex chromosome genes and/or sex hormones could potentiate protective factors in females or harmful factors in males. This proposal is high risk as it goes beyond the simple idea that gonadal hormones are the only players that make females different from males. We break down sex-biasing factors into their component parts (e.g., hormones, sex chromosomes, and sex chromosome genes) and manipulate each component while holding others constant to assess their contribution to the sex difference. Preliminary data in this proposal show that in lung tissue obtained from male patients with idiopathic pulmonary fibrosis (IPF), a fatal form of pulmonary fibrosis more common in middle aged and elderly men, there is a 30- fold increase in androgen receptor (AR) mRNA accompanied by an increase in AR receptor protein. This data strongly support the idea that activation by testosterone could promote downstream fibrotic pathways in an age-associated lung disease like IPF. We hypothesize that a) aging male patients with IPF have more severe lung disease due to androgen receptor-activated fibrotic pathways and b) sex differences in lung fibrosis are caused in part by genes encoded by the sex chromosomes. Discovery of new mechanisms to account for the sex disparity in age-associated lung fibrosis will uncover protective and/or harmful factors that may lead to new diagnostic and therapeutic strategies. To detect sex-specific differential pathways we will perform the following Aims: Aim 1: Determine the activational effects of gonadal hormones/respective receptors and subsequent downstream signaling that contribute to age-associated lung disease. A.These studies gonadectomize (GDX) aging male and female BLM-treated mice to determine if estrogens are protective and androgens harmful to lung fibrosis. B. Determine the contribution of AR and ER in the development of lung fibrosis using myofibroblasts isolated from lungs of male and female patients with IPF. Aim 2: Determine whether sex chromosomes contribute to sex differences in age-associated lung disease using the four core genotypes (FCG) mouse model. This model separates the effects of gonadal sex (ovaries versus testes) from the sex chromosome complement (XX vs. XY) by producing XX and XY gonadal males and XX and XY gonadal females and will be done in collaboration with Dr. Arthur Arnold.